The present invention relates to an optical disk apparatus for reading information recorded on a recording surface of an optical disk or recording the information thereon, and an optical pickup and an optical device used for it, and in particular, to a structure of the optical device using a microfabrication technology.
Optical disk apparatus for recording information on a disk-like recording medium by using light or reading and reproducing the recorded information include CDs such as a CD-ROM, a CD-R and a CD-RW using a light emitting element of a wavelength of approximately 780 nm and DVDs such as a DVD-ROM, a DVD-R and a DVD-RAM using a light emitting element of a wavelength of approximately 650 nm. They are widely diffused by exploiting their respective characteristics. For this reason, it is strongly demanded that one optical disk apparatus is capable of dealing with various optical disks. It is also demanded, accompanying with diffusion of notebook type computers, to miniaturize and thin the optical disk apparatus and an optical pickup. In the conventional optical pickups, a laser light source oscillating at the wavelength of approximately 655 nm, a laser light source oscillating at the wavelength of approximately 785 nm, a prism, a half mirror, a collimator lens, a startup mirror, an actuator, an objective lens, a detection lens, a photodetector (photo acceptance element) and a front monitor are mounted on a case for the optical pickup. The light from the two laser light sources are reflected by on or transmitted through the prism and the half mirror, becomes parallel light through the collimator lens, reflected by the startup mirror, and collected on the optical disk by the objective lens. Reflected light from the optical disk passes through the objective lens, the startup mirror, the collimator lens and the half mirror again, and enter the photodetector after passing through the detection lens. The photodetector is divided into a plurality of light receiving areas in which detection of a focus error signal, a track error signal and a reproduction signal are carried out (for instance, refer to JP-A-2002-269804 (pp. 2 to 3, FIG. 1)).
Fixed positions of a light emitting element, a photo acceptance element, a prism and a half mirror are important when detecting a signal with an optical pickup. Unless they are precisely adjusted to these fixed positions, there arises a problem that the position of light entering the photo acceptance element is deviated and recording and reproducing of the information cannot be accurately performed. In particular, high positioning accuracy of an optical component and so on is demanded in order to secure reproducibility of the information on a disk on recording and on using a high-density recording medium. In the conventional arts, a structure is adopted in which a part of a joint surface of the prism is exposed to abut a holding member such as a case in order to secure position accuracy upon assembling and precise adjustment to the fixed positions. In the conventional art, however, the position accuracy and the precise adjustment are determined by surface accuracy of the holding member such as the case, and the conventional art is not necessarily sufficient to perform stable assembling. Furthermore, an extra space is needed in order to expose a part of the prism. Moreover, in the conventional art, since a packaged laser light source for the light source is used, the conventional art is not sufficient in terms of miniaturization of the apparatus. Moreover, in the case of recording on a CD-R, a DVD-RAM and so on, output of a laser becomes large, and therefore, there is a problem of a temperature rise due to heat generation of the light emitting element.
An object of the present invention is to provide an optical device capable of precisely assembling optical components such as a light emitting element and a prism, and is small and thin and has a good heat radiation even in the case of using a plurality of light emitting elements, and further to provide a small, thin and high-performance optical pickup and eventually such an optical disk apparatus by using the optical device.